Carburetor accelerator pump control apparatus

ABSTRACT

Control apparatus for a carburetor which varies the stroke of the accelerator pump in response to engine temperature. When the sensed temperature is above a predetermined magnitude, a vacuum motor in communication with a source of intake manifold vacuum positions a movable element so as to permit only a partial pump stroke in immediate response to throttle opening. When the sensed temperature is below the predetermined magnitude, the full stroke of the accelerator pump is permitted.

United States Patent [1 1 Baldin et al'.

CARBURETOR ACCELERATOR PUMP CONTROL APPARATUS Inventors: Frede Baldin, Plymouth; George Nastas, Livonia, both of Mich.

Assignee: Ford Motor Company, Dearborn,

Mich.

Filed: Jan. 4, 1974 Appl. No.: 430,822

U.S. Cl 261/34 B; 261/39 B Int. Cl. F02M 7/08 Field of Search 261/34 B, 39 B References Cited UNITED STATES PATENTS Derengowski et a1 261/34 B Baldwin 261/34 B Hebert 261/34 B Bickhaus et a1 261/34 B 1 May 27, 1975 3,486,742 12/1969 Szwargulski 261/39 B 3,752,450 8/1973 Charron ct a1 261/65 3,831,567 8/1964 Freismut'h ct a1. 261/39 B Primary Examiner-Tim R. Miles Attorney, Agent, or Firm'Roger E. Erickson; Keith L. Zerschling [57] ABSTRACT Control apparatus for a carburetor which varies the stroke of the accelerator pump in response to engine temperature. When the sensed temperature is above a predetermined magnitude, a vacuum motor in communication with a source of intake manifold vacuum positions a movable element so as to permit only a partial pump stroke in immediate response to throttle opening. When the sensed temperature is below the predetermined magnitude, the full stroke of the accelerator pump is permitted.

4 Claims, 6 Drawing Figures CARBURETOR ACCELERATOR PUMP CONTROL APPARATUS BACKGROUND AND SUMMARY OF THE INVENTION The accelerator pump of a carburetor is often a mechanical device to supply extra fuel to the engine simul taneously with the opening of the throttle plates during an acceleration. If the accelerator pump is mechanically linked to the throttle the pump stroke will be a function of the throttle movement. It is recognized that an engine needs a greater amount of fuel to be delivered by the accelerator pump under cold engine or ambient conditions than under warm engine or ambient conditions. It is also known in the art to vary the output of a accelerator pump as a function of engine temperature. See for example, U.S. Pat. No. 1,981,969 granted on Nov. 27, I934 to A. M. Prentiss.

This invention provides control apparatus for the accelerator pump of internal combustion engine carburetor which reduces the stroke of the accelerator pump when the temperature sensed by the control apparatus exceeds a predetermined magnitude. The invention also provides a control apparatus which permits the completion of the full stroke of the accelerator pump regardless of temperature if a wide open throttle condition is maintained. Consequently, this invention provides a carburetor which delivers maximum power under accelerating conditions without delivering too much fuel in a given time span and without resulting in excessive engine emissions. This invention also provides an accelerator pump control device which is completely external to a conventional carburetor and which can be installed on a conventional carburetor without significantly changing the carburetor structure. This invention also provides an accelerator pump control system which is economical to produce and install and which is reliable in service.

An accelerator pump control device constructed in accordance with this invention includes a manifold vacuum responsive and temperature sensitive power means having a movable element co-operable with the mechanical linkage extending between the throttle valve and the accelerator pump. The power means positions the movable element so as to permit the linkage to move unrestrictedly when the temperature sensed thereby is less than a predetermined magnitude. The power means positions the movable element so as to limit the displacement of the linkage means in response to throttle valve opening when the temperature exceeds the predetermined magnitude. The power means may include a motion delay means which permits the displacement of the linkage means for the remainder of the full stroke following the interruption of the full stroke by the movable element of the power means when the temperature exceeds the predetermined magnitude. The linkage means then moves through the final portion of its travel in delayed response to throttle valve movement.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of a carburetor assembly including the invention.

FIG. 2 is an enlarged view of the manifold vacuum responsive temperature sensitive power means when the temperature sensed is below a predetermined magnitude.

FIG. 3 is a view similar to FIG. 2 when the temperature sensed is above a predetermined magnitude.

FIG. 4 is a cross sectional view corresponding to FIG. 2.

FIG. 5 is a cross sectional view corresponding to FIG. 3.

FIG. 6 is a side elevational view of the throttle lever assembly.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Carburetor 11 includes a pair of induction passages 13 and 15 and a pair of throttle plates 17 and 19 pivotally mounted within the induction passages. The throttle shaft 21 has a lever 23 fixed to the end of it. A second lever 25 is positioned about the throttle shaft but is not fixed to it. The second lever is biased into engagement with the first or throttle lever by a torsion spring 27. The first lever and the second lever move together as a unit as through they were fixed until the second lever 25 engages an abutment 36. When this condition occurs, further displacement of the first lever 23 results in increased torsional windup of spring 27.

The carburetor includes an accelerator pump 29 which injects fuel directly into the induction passages as the throttle plates begin to open. The accelerator pump includes a lever 31 pivotable about a point 33 and connected to second lever 25 by a pinjoined link 35. It can be seen that the first lever 23 and the accelerator pump lever 31 are directly mechanically connected and move simultaneously during the first portion of throttle movement and cease moving simultaneously only when point 34 of the second lever engages abutment 36 or the accelerator pump lever reach the end of its range of permissible movement. When this point occurs, the first lever 23 continues to move but is acting against the torsional force of the spring 27.

To permit the stroke of the accelerator pump 29 to be tailored or varied in accordance with engine temper ature and intake manifold pressure conditions, a manifold vacuum responsive and temperature sensitive power means is provided. It is the function of the power means to position and displace a movable element 39 in response to intake manifold conditions. The main portion of the power means is mounted to the carbure tor body by a suitable bracket (not shown).

FIG. 2 of the drawings illustrates the relationship of the movable element 39 of the power means and the lever 31 of the accelerator pump when the engine temperature is below a predetermined level (e.g., F.) and the throttle plates are in closed or nearly closed positions. The movable element is then fully protracted from the body of the power means and a tab of pin 41 depending from the end of lever 31 is free to move the entire length of the slot 43 of the movable element 39 if an acceleration were to occur. Accordingly, when the temperature is below the predetermined value, the accelerator pump lever is permitted to move a full stroke length and a full measure of fuel is delivered to the induction passages in immediate and direct response to throttle lever opening displacement.

FIG. 3 of the drawings illustrates the relationship of the movable element 39 of the power means and the accelerator pump lever 31 when the temperature sensed by the power means exceeds the predetermined magnitude and the throttle valves are in closed or nearly closed positions. It can be seen that the movable element is in a retracted position and that the tab 41 of the accelerator pump lever is free to move only in a portion of the slot 43. Thus, only a partial stroke is permitted and a partial measure of fuel is delivered when the movable element is in the position as shown in FIG. 3. After the tab 41 hits the right-hand end of the slot as seen in FIG. 3, additional opening movement of the throttle lever results in increased compression of the torsion spring 27 and relative movement between first lever 23 and second lever 25. When the movable element is in the position of FIG. 3 and the engine is accelerated and the throttle valve is held open for a sustained period of time in a wide-open throttle position, the movable element moves rightwardly in a controlled and delayed manner and permits the accelerator pump to complete its full stroke.

The manifold vacuum responsive and temperature sensitive power means 37 is shown in detail in FIGS. 4 and of the drawings. The power means includes a main housing 45, and end housing 47 and a flexible diaphragm 49 clamped therebetween. A guide 51 is secured within an opening in the end housing and includes a bore 53 which slidably receives movable element 39. The movable element is connected to retainers 55 and 57 which sandwich the central portion of the flexible diaphragm and act as abutments to limit the axial movements of the diaphragm. A spring retainer 59 is positioned within the main housing and with retainer 55 confines a compression spring 61. A second compression spring 63 having a stiffness of less than that of spring 61 is confined between the other side of retainer 55 and a bimetal disc 65. The bimetal at temperatures below the predetermined temperature is in a flat conditon and overlies a sintered orifice 67 formed in an umbrella valve 69. The umbrella valve is mounted to a disc element 71 having a plurality of openings 73. The disc element is snap fitted or staked into position within an annular groove formed in the housing 45. A seal or gasket 75 is sandwiched between the disc element 71 and a parallel surface 77 of the main housing to provide a peripheral seal between the housing and the disc 71. The umbrella valve, in its relaxed state, overlies and blocks the openings 73. The prechamber or volume 79 between the umbrella valve 69 and the bimetal 65 is communicated to the main chamber 81 of the power means by a restricted orifice 83. The orifice permits the controlled and limited of air flow between chamber 79 at intake manifold vacuum pressure and the main chamber 81 of the power means. The chamber on the opposite side of the flexible diaphragm 49 is always at atmospheric pressure vented through ports 85. Passage 87 is connected to a source of intake manifold vacuum.

OPERATION When the temperature sensed by the bimetal disc 65 is less than the design temperature (e.g., 60F.) the bimetal is in a flat position or bowed leftwardly so as to engage and close the orifice 67 as shown in FIG. 4 of the drawings. The force of the spring 61 positions the movable element 39 in its fully protracted position. When an acceleration occurs and the intake manifold experiences a loss in vacuum pressure, the closed bimetal disc 65 prevents the vacuum decay of chambers 79 and 81 of the power means so that the movable element 39 stays in its extended or protracted position and the accelerator pump 29 is permitted its full stroke.

When the engine is warm and the power means senses a temperature in excess of the design temperature, the bimetal disc 65 is bowed or bulges rightwardly and the prechamber 79 is in communication through the open orifice 67 and the passage 87 with the source of intake manifold vacuum. The vacuum signal is communicated to the main chamber 81 through restricted passage 83. While the throttle valves 17 and 19 are closed or substantially closed, the vacuum signal is of sufficient magnitude to overcome the force of spring 61 and to cause the diaphragm assembly and element 39 to move leftwardly so that the movable element is in the retracted position as shown in FIGS. 3 and 5. The accelerator pump lever 31 is permitted only a portion of its full range of travel before tab 41 abuts with the righthand end of slot 43. Consequently, the quantity of fuel delivered to the induction passage in direct or immediate response to throttle opening movement is reduced relative to the quantity delivered when the sensed temperature is below the design temperature. If the open throttle condition is maintained, the pressure differential across the restriction passage 83 dissipates within a predetermined time. The force of spring 61 acting in opposition to the pressure differential across the diaphragm 49 then moves the diaphragm assembly and movable member 39 in a rightwardly direction until the entire pressure differential between the main chamber 81 and the source of intake manifold vacuum is dissipated. At this time the movable element 39 is in its fully extended position. The accelerator pump lever 31 bearing against the right-hand end of the slot 43 as it moved rightwardly has caused the accelerator pump 29 to complete its full stroke. The partial immediate accelerator pump stroke and the retarded completion of the stroke prevents the overloading of the carburetor with fuel that cannot be immediately utilized and which would otherwise result in overrich combustion and increased engine emissions. When the acceleration is completed and the throttle returns to a more nearly closed position and a full or moderate intake manifold vacuum is restored, the vacuum pressure within the chamber 81 is likewise restored and the movable element 39 is again withdrawn to its retracted position.

The specific funtion of the umbrella valve 69 is to immediately release the vacuum from chamber 79 upon stopping the engine. This permits the accelerator pump 29 to fill more quickly and be prepared for a restart in the event of a cold stall.

Modifications and alterations will occur to those skilled in the art which are included within the scope of the following claims.

We claim:

1. In an internal combustion engine having a carburetor including an induction passage, a throttle valve pivotally mounted within said induction passage, an accelerator pump to inject fuel into said induction passage, linkage means interconnecting said accelerator pump and said throttle valve so that movement thereof results in actuation of the accelerator pump,

a manifold vacuum responsive and temperature sensitive means having a movable element cooperable with said linkage means to limit the displacement thereof in response to throttle valve opening when the sensed temperature exceeds a predetermined magnitude,

said linkage having elements including a first lever movable with said throttle valve,

a second lever that actuates the accelerator pump,

a resilient member and a solid link interconnecting said first and second levers said resilient member being preloaded so as to act as a solid member until the second lever reaches the end of its travel,

said manifold vacuum responsive and temperature sensitive means including a housing,

said movable element having a slot formed therein extending longitudinally in the direction of movement of said movable element, said movable element being retractable so that said slot is partially received within said housing,

said movable element being protracted and said one element of said linkage means being movable within the full length of said slot upon an acceleration when the temperature is below said predetermined magnitude,

said movable element being retracted and said one element of said linkage means being movable within the exposed portion of said slot upon an acceleration when the temperature exceeds said predetermined magnitude.

2. In an internal combustion engine, apparatus according to claim 1,

said manifold vacuum responsive and temperature sensitive means including a vacuum motor,

said vacuum motor including a housing defining an enclosure, a flexible diaphragm dividing said enclosure into first and second chambers, said movable element connected to said flexible diaphragm and movable therewith in response to changes in pressure differentials between said chambers,

passage means connecting one of said chambers to a source of intake manifold vacuum, vent means communicating the other of said chambers to the atmosphere,

a bimetal element opening said passage when the temperature within the enclosure exceeds said predetermined magnitude and closing said passage when the temperature within the enclosure is below said predetermined magnitude.

3. In an internal combustion engine, apparatus according to claim 1,

said manifold vacuum responsive and temperature sensitive means including a motion delay means,

said manifold vacuum responsive and temperature sensitive means positioning said movable element so as to permit the displacement of said linkage means in direct response to throttle valve movement during the first portion of throttle valve opening when the temperature exceeds said predetermined magnitude and to permit the displacement of said linkage means in delayed response to throttle valve movement following the latter portion of throttle valve opening.

4. In an internal combustion engine, apparatus according to claim 2,

said manifold vacuum responsive and temperature sensitive means including a pressure decay means, said pressure decay means comprising a restriction within said passage means preventing immediate pressure equalization between the intake manifold and said one chamber. 

1. In an internal combustion engine having a carburetor including an induction passage, a throttle valve pivotally mounted within said induction passage, an accelerator pump to inject fuel into said induction passage, linkage means interconnecting said accelerator pump and said throttle valve so that movement thereof results in actuation of the accelerator pump, a manifold vacuum responsive and temperature sensitive means having a movable element cooperable with said linkage means to limit the displacement thereof in response to throttle valve opening when the sensed temperature exceeds a predetermined magnitude, said linkage having elements including a first lever movable with said throttle valve, a second lever that actuates the accelerator pump, a resilient member and a solid link interconnecting said first and second levers, said resilient member being preloaded so as to act as a solid member until the second lever reaches the end of its travel, said manifold vacuum responsive and temperature sensitive means including a housing, said movable element having a slot formed therein extending longitudinally in the direction of movement of said movable element, said movable element being retractable so that said slot is partially received within said housing, said movable element being protracted and said one element of said linkage means being movable within the full length of said slot upon an acceleration when the temperature is below said predetermined magnitude, said movable element being retracted and said one element of said linkage means being movable within the exposed portion of said slot upon an acceleration when the temperature exceeds said predetermined magnitude.
 2. In an internal combustion engine, apparatus according to claim 1, said manifold vacuum responsive and temperature sensitive means including a vacuum motor, said vacuum motor including a housing defining an enclosure, a flexible diaphragm dividing said enclosure into first and second chambers, said movable element connected to said flexible diaphragm and movable therewith in response to changes in pressure differentials between said chambers, passage meanS connecting one of said chambers to a source of intake manifold vacuum, vent means communicating the other of said chambers to the atmosphere, a bimetal element opening said passage when the temperature within the enclosure exceeds said predetermined magnitude and closing said passage when the temperature within the enclosure is below said predetermined magnitude.
 3. In an internal combustion engine, apparatus according to claim 1, said manifold vacuum responsive and temperature sensitive means including a motion delay means, said manifold vacuum responsive and temperature sensitive means positioning said movable element so as to permit the displacement of said linkage means in direct response to throttle valve movement during the first portion of throttle valve opening when the temperature exceeds said predetermined magnitude and to permit the displacement of said linkage means in delayed response to throttle valve movement following the latter portion of throttle valve opening.
 4. In an internal combustion engine, apparatus according to claim 2, said manifold vacuum responsive and temperature sensitive means including a pressure decay means, said pressure decay means comprising a restriction within said passage means preventing immediate pressure equalization between the intake manifold and said one chamber. 